Ballistics Aurgument Rational
 

Hey Guys,

So for years now it always comes up .270 better than this or that. etc....

When deciding what is better than another where does bullet weight come into play?

Said another way, how can we compare a .270 to a .308 if they shoot completely different bullets?

Should retained energy be the measurement?

On another level I'm wondering since there appears to be lots of factors, kick, bullet weight, amount of powder, trajectory etc... if there couldn't be a mathematical model that quantifies a cartridge. Basically every cartridge gets a number based on it's factors. Does this make any sense?

Ok I'm done rambling let me have it.

Tom

RE: Ballistics Aurgument Rational
 

I'm not sure if its what your talking about but there is a comparison tool called the Taylor KO factor.So in your comparison of a 270 and 308 if they both are shooting 150gr bullets,with the 270 at 2850fps the TKO is 16.92 and the 308 at 2936fps the TKO is 19.38. Load data taken from the IMR loading data online. I'm not sure what the numbers give you other than a basis for comparison based on the bullet weight, velocity and caliber.

RE: Ballistics Aurgument Rational
 

what you are asking for already exists. But, like most things its not nearly as simple as we would like them to be.

How do we compare cartridges with different bullets? You must use sectional density. To properly compare two cartridges of different diameter bullets you must compare bullets of similar SD. for example a .270 140gr. bullet has a SD of aprox. .26 to compare a .30 150gr. has a SD of aprox. .26

Now you can compare the two.With this in mind you can Look at the muzzle velocities, kinetic energies, trajectories...... Recoil is so subjective I don't have any clue as to how to quantify it. I know that there are measurement in foot pounds etc. But what is manageable to one person can be unbearable to another.

I will tell you this, you won't find a nickels worth of difference between them anywhere but on paper. In the real world of average shooters at average distances game animals are just as dead with one as the other. The rest of the arguments are just bored hunters trying to fill their time until the next hunt begins.

RE: Ballistics Aurgument Rational
 

Good post. Especially the last paragraph.

RE: Ballistics Aurgument Rational
 

Shato said it just right. SD is the way to compare bullets of different calibers to each other There are to many other differences to make this the one and only method but at ranges to 300 yards there are a truck load of cartridges that will perform the same task equally well. One other component is to compare bullets of the same shape and construction. Such as using the Partition in all calibers for comparison.

RE: Ballistics Aurgument Rational
 

Remington and Winchester both show their 150 gr. .270 loads at 2850 fps, and their 150 gr. .308 loads at 2820 fps. He said he was using IMR's reload data, so I suspect there's may be a pretty wide range of combinations for each rifle... Perhaps the .308 load he was looking at was a "light magnum" load, vs. a standard .270 load.

RE: Ballistics Aurgument Rational
 

So how can a .270 be compared to a .308 when a .308 can launch heavier bullets but a .270 cannot?

For the record I know this is just a bunch of boo haa because they all work inside of 300 yds. Just trying to figure out if it even makes sense to make a comparision in the first place.

Tom

RE: Ballistics Aurgument Rational
 

You compare the two by using the 150 grain 270 and the 180 grain 308. You can expect these two bullets to perform about the same job because they have the same SD. Both will penetrate about the same and in this case the velocities and ME are in the same ball park.

The taylor KO fomula will give you a good tool to compare even though its not perfect and leans toward Heavier bullets.

RE: Ballistics Aurgument Rational
 

What about ballistic coefficient and drag coefficient?

The "closeness" of a bullet to the mathematically "perfect" bullet has to play into bullet efficiency and thus cartridge efficiency at some point. See Krupps Standard Reference Projectile.

There are some basic models out there and I believe they were developed by the Army's Ballistics Research Lab. You've probably seen them in small ballistic programs usually they are called something like G1, G5, G7, etcdrag coeffiecient models.

The short comings of those early models gave rise to the BC or ballistic coefficient, bullet form factorand the sectional density models which helped relate different bullet shapes and sizes to the drag models. Which is why we generally use Ballistic Coefficient as a measure of how much "better" a bullet is moving through the air.

So SD is not the product we want to look at. It's a component of BC which is what we currently use to compare bullets.

Ballistic Coefficient = (Bullet Sectional Density) / (Bullet Form Factor)

I'm sure computational fluid dynamics has been applied to conventional rifle cartridges and there is a model and I'm sure it uses a number of variables to spit out a betterproduct but the question remains: how do you define "better"? Also, what assumptions is your model based upon? The answers, if there are any, have an enormous effect on how and what your model shows, and if those findings are worth anything in the real world.

Also, a complex fluid dynamics model that approached anything relative to real world performance may not even be able to be ran on anything short of a mini-supercomputer. And certainly not a normal PC.

Now that all applies to exterior ballistics.

If you're talking about terminal ballistic performance, no I don't believe there is any model for terminal ballistics. At least one that would produce anything worthwhile or close to reality. The inherent stochasticityand sheer volume of variables of such a model would be impossible to simulate in my opinion.

RE: Ballistics Argument Rational
 

There would be no end to the things that complete the whole picture. The question here was just how to compare bullets of different wights and caliber. To compare you would need to use the same bullet as well. Like the Nosler partition which has the same shape and construction in all caliber. I am a hunter not a scientist or ballistics engineer. I have however killed big game in the field with probably 20 different calibers. I don't know everything about why things work but I do know what does work and what does not.

RE: Ballistics Aurgument Rational
 

Retained energy really doesn't tell you much, because kinetic energy cannot be directly related to killing effect. For example, a .308 Winchester will produce much greater kinetic energy than a .54-caliber pure lead round ball launched as fast as a muzzleloader can launch it, yet the round ball will also do a creditable job of killing game.

In addition, although I can understand your desire to develop a "formula" that will permit you to calculate the usefulness of a given cartridge or compare cartridges, I do not believe this is really possible, since so many of the factors are more subjective than real. Many have tried in the past, yet the results of such labors is questionable at best. For example, you can calculate the free recoil of a specific load in a gun of given weight, but this number does not indicate how that recoil "feels" to an individual shooter. Some find the recoil of a .30/'06 to be objectionable, but that same person has no problems with the recoil fo a 12-ga. 3.5" magnum goose loadthat in reality delivers three times the free recoil of a .30/'06!

IMO, when one is shooting any of the medium-power cartridges between .243" and .323" (6mm to 8mm) in caliber, using bullets of like construction and similar sectional density, if one places his/her shots correctly, the actual difference in results when shooting the same game is largely academic.

As a matter of fact, arguing which is better, a .308, .30/'06, 7X57mm, 7mm/'08, .270 or .280, etc. etc., is about as sensible as debating how many angels can stand on the head of a pin. A lot of fun, perhaps, but not much else.

RE: Ballistics Aurgument Rational
 

DGH thinks Brutal Attack has way too much off time on his hands :D Actually, everything he said is correct, but Shato Davis said it better.

I use the common sense comparison - will the rifle shoot a bullt that kills my game at the range I hunt - if the answer is yes, comparison done:)

As to load data for the 270 vs .308 - it completely depends on what you buy, or load. The Hornady light mags for .308 are 3,000 fps for 150 grain BTSP and 2,880 for 165 grain BTSP:) And, I guess load data opens a whole new can of worms - huh; and barrel length, weight of rifle = felt recoil, bullet selection, placement of bullet, range to game, etc.

I don't get to hunt until Saturday, so very bored deer hunter here

RE: Ballistics Aurgument Rational
 

I only want add one thing to all the good replies here. I recently have gotten back into reloading, well I say that but in reality all I loaded for was my 7mm mag. about 18 years ago. Although I have loaded thousands of shotgun rounds.But anyway, I own a .300 win mag, a 30-06, a 35 rem. and that 7mm, and have also killed deer with the .270 and the ole 30-30. I love all my guns and greatlyenjoy using them, but when you really get to studying reloading you begin torealize that all a person really needs is the 30-06, or better yet the .308. Honestly, I think that if all hunters/shooters took the time to study reloading their jaws would hit the floor thinking to themselves "why am i shooting this super duper latest greates ultra super butt kicking magnum".

RE: Ballistics Argument Rational
 

You got that right. Out to 300 yards which is out to about the max that the average hunter can hit the kill zone. 200 hundred may be close yet. When you exceed that range then there is some benefits to rifles like the 300 mags and such. And again, the calibers from 6.5 on up will all do the job in the hands of a decent hunter. I would not suggest that the gun companies stand still and not strive to make good products or new products, thats how we got where we are today. However, beyond 400 yards, things really get iffy and the hunter who can not practice at those ranges really should not even attempt such shots. Even practice won't remove the effects of wind heat vapors,altitude and animal movement and much more.